Question about HVAC relocation bracket/ Tip on aux/usb extension item

Hello, I uinderstand the difference between all the relocation brackets needed for a double din retrofit as stated in wonderful write ups such as Wolfn8tr's exceptional installation post (http://ift.tt/19INhed) on the eonon unit (the ga5150 is the unit I am a click away from purchasing). Anyway, I wanted to know if purchasing a relocation bracket is really even necessary? I have the oem business head unit so I'm not asking this because my car came with the double din navigation head unit. I just wanted to know what's stopping you from just popping out the sun glass tray and inserting the hvac unit directly into the open space? It is just aesthetics, as in there might be a miniscule gap? Does the original bracket containing the sunglass tray not carry the necessary moutning points for the hvac unit? I really just want to know if buying a relocation bracket is really necessary considering the sun glass compartment looks like it would work...



Also somewhat related I found these "Car mount USB extensions" which I think will come in handy for those people who hve purchased avin/dynavin/eonon units as it extends the aux jack and usb port as stated straight from the rca cables in a neat little package. (I planned to make the hole for it in my coin tray)

http://ift.tt/1CS7KVc



Any answers would be appreciated,

Thank you